By Joseph Gallegos with C. Y. Fraser
Drought tolerant landscapes are beautiful and serve a purpose. It was needed as part of a media campaign during the drought to remind the public to conserve water. However now, we are faced with the results of this temporary remedy to our water conservation efforts.
Drought Tolerant (DT) landscapes by nature create heat islands in our urban environment. They cover less soil thereby exposing more dirt, stone or hard surfaces (like DG – decomposed granite) to bake under the sun. This small layer of crusting has a big impact. It creates stronger soil surface tension leading to a hydrophobic condition: repelling of surface water. This is why on those days when you water, you can spend an hour and the water penetrates just the top 1/16th inch of soil. When you walk over this wet soil, your shoes pick up mud, exposing dry foot prints because there is no absorption or delivery of moisture past the hydrophobic layer. This leads us to two important concerns. One, hydrophobic soil surfaces do not allow rain to percolate. Instead it increases rain run off. Two, small particle pollutants that land on soil surfaces cannot bind with dirt, thus remain free to blow in the wind leading to bad air quality days.
What is needed is another strategy for greener landscapes in urban areas to clean the air, absorb rainwater and secure pollutants in our atmosphere. Like trees recycling CO2 to oxygenate the air we breathe, greywater from regularly used shower and laundry water can also help clean the air by irrigating lush, green landscapes, which in turn decrease heat islands, sequester carbon, and bind small particle pollutants.Together greenscapes and greywater not
only conserve water, but encourage a greener, cleaner, more urban friendly environment.
Lush green landscapes are the path to a healthy urban environment, even if it is different from what was advocated during the drought. The greener solution is innovative greywater reuse for landscape irrigation. Wouldn’t you prefer to feel a cool breeze flowing from your forested lawn over a decomposed granite heat island?